The Fire shard gives access to fire related spells.
This spellstone is found near the NPC character Ko.
There is a small hut on the island, with a stone archway, where you will see Ko standing. The fire shard is near the edge of the cliff near Ko.
The first spell, burning hands, is a close-range spell that constantly does 1-2 damage on a single target. The spell is generally hard to use, and is not typically effective in battle.
The second spell, fireball, launches a ball of fire at an opponent. The spell is difficult to aim, but does approximately 35 damage per strike, making it incredibly effective upon contact with an enemy. In addition,it does AOE damage, which means it will damage all enemies in a certain distance around the area where the fireball directly hit.